Irrigation and Drainage Engineering Flashcards
CLSU - Part 2
artificial application of water to the soil necessary to supply the moisture essential for plant growth.
Irrigation
removal of excess water from the soil that is detrimental to plants.
drainage
art of measuring horizontal and vertical distances between objects, of measuring angles between lines, of determining the direction of lines, and of establishing points by predetermined angular and linear measurements.
surveying
a natural process of adding moisture to the soil but it can result to excessive water
rainfall
determined from the data of the survey
Distances, angles, directions, locations, elevations, areas, and volumes
portrayed graphically by the construction of maps, profiles, cross sections, and diagrams
survey data
consists of counting the number of steps or paces in a required distance.
Distance by Pacing
Made to lay out, locate and monitor public and private engineering
works.
Construction Survey
type of surveying that takes into account the true shape of the earth. These surveys are of high precision and extend over large areas.
Geodetic Surveying
Made to gather data to produce a topographic map showing the configuration of the terrain and the location of natural and man-made objects
Topographic Survey
The survey of bodies of water made for the purpose of navigation, water supply, or sub-aqueous construction.
Hydrographic Survey
type of surveying in which the mean surface of the earth is considered as a plane, or in which its spheroidal shape is neglected, with regard to horizontal distances and directions.
plane surveying
Made to establish the horizontal and vertical positions of arbitrary points.
control survey
Made to utilize the principles of aerial photogrammetry, in which measurements made on photographs are used to determine the positions of photographed objects.
Photogrammetric Survey
Made to determine the length and direction of land lines and to establish the position of these lines on the ground
Boundary Survey
Made to control, locate and map underground and surface works related to mining operations.
Mining Survey
equivalent to two paces or a double step.
stride
provides a rapid means of determining horizontal distances.
Stadia Method
The equipment for stadia measurements consists of a telescope with horizontal hairs called stadia hairs and a graduated rod called
stadia rod
The most commonly used devices are odometer, measuring wheel, and the optical rangefinder, these are called______
Distance by Mechanical Devices
the process of determining the extent, size or dimensions of a particular quantity in comparison to a given standard. In surveying, __________ are usually concentrated on angles, elevations, times, lines, areas and volumes.
measurements
a comparison of the measured quantity with a standard
measuring unit or units employed for measuring a quantity of that kind.
Direct measurements
controls, topographic, and construction surveys necessary for the location and construction of highways, railroads, canals, transmission lines, and pipelines.
Route Survey
based on the optical geometry of the instruments employed and is an indirect method of measurement
Distance by Tachymetry
unknown distances may be determined through their relationship with known distance geometrically. These methods are widely employed in plane table surveys, and in triangulation work.
Distance by Graphical and Mathematical Methods
is a simple device that can be attached to a wheel for purposes of roughly measuring surface distance. It is similar in function to the distance recorder of a vehicle speedometer
odometer
defined as an angle subtended by an arc of a circle having length equal to the radius of the circle
radian
the process of directly or indirectly measuring vertical distances to determine the elevation of points or their differences in elevation.
Leveling
when it is not possible to apply a measuring instrument directly to a quantity to be measured an __________ is made
Indirect measurements
refers to the measurement of images on a photograph. The type of photographs used are those taken from an aircraft with the axis of the camera pointed vertically towards the terrain photographed
Distance by Photogrammetry
very similar in operation to an odometer except that it is more portable and self-contained measuring device. It is basically consists of a small wheel which is attached to a rod and handle, and can be pushed by an operator.
Measuring Wheel
Tachymetric measurements are performed either by ______ method or the _____ method
stadia, subtense bar
most common method of measuring or laying out horizontal distances. ______ consists of stretching a calibrated tape between two points and reading the distance indicated in the tape.
distance by taping (taping)
used in design highways, railroads, canals, sewers, water supply systems; layout construction projects according to planned elevations;
Leveling results
urved surface which is at any point perpendicular to the direction of gravity or the plumb line.
Level surface
operates on the same principle as a rangefinder on a single-lens reflex camera. This device, which is usually hand-held or mounted on a small tripod, can be used to determine distances approximately simply by focusing
Optical Rangefinder
a curved line in a level surface, all points of which are normal to the direction of gravity and equidistant from the center of the earth.
Level line
a straight line in a horizontal plane which is tangent to a level line at one point.
Horizontal line
a plane that is tangent to a level surface at a particular point.
Horizontal surface
a fixed point of reference whose elevation is either known or assumed. They maybe permanent or temporary.
Bench Mark (BM
at any point is a line parallel to the direction of gravity.
Vertical line
an imaginary surface of the sea which is midway between high and low tides.
Mean sea level
any convenient level surface coincident or parallel with mean sea level to which elevations of a particular area are referred.
datum
are those which established at intervals throughout the country by the Philippine Coast and Geodetic Surveys (PCGS) or the Bureau of Lands.
Permanent BM
the vertical distance between the two level surfaces in which the points lie.
Difference in elevation
the vertical distance above or below mean sea level or any other selected datum
Elevation
are those set up by the surveyor for his own use in a particular surveying project and may have assumed elevations.
Temporary BM
the process of determining the difference in elevation between two or more points some distance apart.
Differential Leveling
reading taken on a rod held on a point of known or assumed elevation. It is a measure of vertical distance from the established line of sight to the point sighted (+S).
Backsight (BS)
used to establish changes in elevation along a line.
Profile Leveling
an intervening point between two BMs upon which point foresight and backsight rod readings are taken to enable a leveling operation to continue from a new instrument position.
Turning Point (TP)
a reading taken on a rod held on a point whose elevation is to be determined (-S).
Foresight (FS)
is an electronic transit and an electronic distance measuring (EDM) combined into one instrument.
Electronic Total Station
the aerial photos are prepared as a raster of pixels (picture elements), each of which has its raster row and column location and its density, stored digitally.
DPS (Digital Photogrammetric System)
Common lines requiring surveying are ______
drains, roads, fences, and retaining walls
the elevation of the line of sight of an instrument above or below a selected reference datum.
Height of Instrument (HI)
used to measure distance using lasers. Laser range finders are called electronic distance measuring (EDM).
Range Finder
The hydrologic cycle may be viewed as beginning with ________, the movement of water
from the liquid to the vapor state, from any wet surface
evaporation
The system is based upon observations made on electromagnetic signals transmitted from a constellation of 24 satellites, each of which circling the earth in a precisely known orbit.
GPS (Global Positioning System)
change of water from vapor to liquid
condensation
change of vapor to ice
sublimation
form clouds, which may, in turn, fall to earth
precipitation
The precipitation may be dispersed in several ways: Be evaporated while falling _____
virga
The precipitation may be dispersed in several ways: Be _______ by vegetation cover or by surfaces of buildings and other structures, and then be evaporated back into the atmosphere rather quickly
intercepted
The precipitation may be dispersed in several ways: Water not intercepted by vegetation is
termed _______
throughfall
The precipitation may be dispersed in several ways; Flow over the surface
overland flow
The precipitation may be dispersed in several ways: discharge into streams and lakes
surface runoff
The precipitation may be dispersed in several ways: move by evaporation into the atmosphere or by seepage towards the _______ or by further flow into the oceans
groundwater
The precipitation may be dispersed in several ways: _____ through the ground surface to join existing soil water and be removed by evaporation from the soil, or by _____ towards stream channels (subsurface flow or _____), or by downward _______ to the underlying groundwater where it may be held from weeks to millennia.
Infiltrate, throughflow, interflow, percolation
a gradual process in which something is changed from liquid to gas.
Evaporation
the scientific study of the waters of the earth including their occurrence, distribution in space and time, and their relation to people and the natural environments
Hydrology
biological process in which water evaporates from a plant, especially through tiny openings called stomata on the surfaces of leaves.
Transpiration
a process by which vapor lose heat and changes into a liquid
Condensation
rain, snow, or hails, all of which are formed by condensation of moisture in the atmosphere and fall to the ground.
Precipitation
the combined process of transpiration by the plant, and evaporation from the soil or free water surface.
Evapotranspiration
movement of water through the soil surface into the soil
Infiltration
to make a liquid or gas pass through a porous substance.
Percolation
a chemical process in which a solid substance is converted into a gas directly, without passing through an intermediate liquid phase.
Sublimation
the horizontal transfer of a property such as heat, caused by air movement
Advection
horizontal or lateral movement of water below the soil surface.
Seepage
water not absorbed by the soil and flows into surface waters
Runoff
paramount importance in the transformation of water from vapor to liquid or solid state and also in effecting favorable or unfavorable environmental conditions for man, animals or plants
Role of Climatological Elements
amount of water that falls over the land or water bodies and is sometimes referred to as precipitation.
Rainfall
water movement below the water table from groundwater storage to a channel or river.
Interflow
movement of water underneath the soil surface from higher to lower elevation or pressure
Groundwater flow
amount of invisible water vapour contained in the atmosphere, an important element in agriculture industry and human comfort. In combination with temperature and wind, the degree of moisture in the air determines the evaporation
Humidity
water retained in potholes, small depressions and other land irregularities.
Overland storage
is part of rainfall intercepted in plant body, physical structures, etc.; it is loss of water by direct evaporation.
Interception
Subsurface components refer to those which become invisible – ____________. All these components occur below the ground surface.
infiltration, seepage, percolation and groundwater or aquifer flow
degree of hotness or coldness of the environment as measured by air thermometer.
Temperature
has chemical, microbiological and physical properties that determine its various functions
soil
determines the rate of air drying and the layout or design of buildings.
Wind speed and direction
these two elements are interrelated, the amount of solar radiation received by the earth’s surface is dependent upon sunshine duration. On the average, about _____ calories cm^-2 day^-1 is received by the earth’s surface and about 50% is used to vaporize water.
Solar radiation and sunshine duration, 400
The amount of water the soil can hold depends upon the _______
physical properties
a storehouse of plant nutrients, a habitat for bacteria, an anchorage for plants, and a reservoir of moisture needed by the plant.
soil
different soil layers from top to bottom is referred to as _____.
soil profile
the two most important physical properties of soil
Soil texture and soil structure
relative proportion of various particles size groups of minerals. based on different combinations of sand, silt and clay particles
soil texture
- after plowing, allow enough time for soil and air to interact before pre-irrigating
- return all possible organic matter to the soil
- plow below compacted layer, not at the same depth each layer
- follow a good crop rotation scheme
important practices to improve the soil structure of irrigated soils
This property refers to the physical condition of the soil in relation to plant growth and ease of tillage. Soils in good tilth are crumbly, easily worked and readily take up water and dry.
Soil Tilth
manner in which soil particles are arranged in group or aggregates. influences the rate at which water and air and move through the soil. It affects root penetration and soil nutrition.
soil structure
For most soils with LOW ORGANIC MATTER content the value closely approaches an average of _____ and those with HIGH ORGANIC MATTER content the value may range from ________.
2.65, 1.5 to 2.0
the attraction of water molecules to each other
Cohesion
results of previous studies serves as the basis for empirical equations using climatic elements as variables. The type and accuracy of data available determine the suitable empirical equation for a given situation.
Effect of climate
refers to the ratio of the density of a single particle to the density of a volume of water equal to the volume of the soil particle. It is also known as PARTICLE DENSITY
Real Specific Gravity (Rs).
Three classes of water have been recognized depending upon the ease at which water is held by the soil
Gravitational water, Capillary water, Hygroscopic water
the ratio of the weight of the given volume of dry soil, air space included, to the weight of an equal volume of water
Apparent Specific Gravity (As).
water that moves freely downward under the influence of gravity through the larger soil pores.
Gravitational water
measure of the forces with which the water is retained in the soil. It is normally expressed in atmospheres based on the average air pressure at sea level
Soil moisture tension
also called volume weight of bulk density with a unit in grams per cubic centimeter or mass per unit volume.
Apparent Specific Gravity (As)
the attraction of soil particles surface to water.
Adhesion
influence the water holding capacity and the movement of water, air and roots through the soil.
Pore spaces
This parameter represents the soil moisture content when the plants starts permanent wilting. It is the lower end of the available moisture range.
Permanent Wilting Point
The soil moisture is generally considered to be ____ atmosphere for most soils.
15
or insufficient water within the rootzone will greatly affect the performance of the plant.
Excessive water (waterlogging)
refer to the portion of available moisture most easily extracted by plants which is approximately 75% of the available water or moisture
readily available moisture
water present in smaller pores that moves slowly due to capillary forces and can move in any direction of greatest tension.
Capillary water
water held so tightly on the particles and the surface that much of it is non-liquid and moves as vapor. It is not available for plant use.
Hygroscopic water
The moisture content held between the field capacity and permanent wilting point is referred to as ______
available moisture or water
parameter represents the threshold between gravitational water and capillary water._______ is the moisture content of the soil remaining after gravitational water has been removed
Field capacity
Soil moisture tension is normally between _______ atmospheres when the soil is at field capacity.
0.1 and 0.3
maximum amount that can occur for a given environmental condition in which the water is not limiting.
potential evapotranspiration (PET)
process by which water is removed from the soil by a plant through the leaves and lost to the atmosphere.
Transpiration
approximately
the difference between the soil moisture content at field capacity and wilting point
Total Available Water (TAW).
refers to the sum total of transpiration through leaves of plants and evaporation from adjacent soil, water surfaces or from surfaces of the plant body.
Consumptive use
the degree to which the amount of water in the soil is allowed to be depleted before the next irrigation is applied.
Management Allowed Deficit (MAD)
the depletion of soil moisture below field capacity at the time that a particular soil moisture content, Pd, is measured.
Soil Moisture Deficit (SMD).
the most crucial factor affecting surface irrigation. This single parameter essentially controls not only the amount of water entering the soil, also the advance rate of the overland flow
Infiltration
Measurement and Monitoring of Soil Moisture
- Gravimetric Method or Oven-drying Method
- Feel and Appearance Method
- Electrical Method
- Tensiometer Method
- Neutron Dispersion Method
Consumptive use is sometimes referred to as
reference crop evapotranspiration (ETo)
diffusion of water as a vapor surface from the surface into the atmosphere.
evaporation
given by the so called crop coefficient which adjust the reference crop evapotranspiration to the actual crop ET.
Effect of crop characteristics
complex process dependent on soil properties, physical properties, initial soil moisture content, previous wetting history, permeability changes due to the surface water movement, and air entrapment
Infiltration
contains terms which account for plant type, plant growing period, mean temperature, and seasonal and latitudinal variations in theoretical solar radiation
Blaney-Criddle Equation
these conditions and practices include variation of climate over time, size of fields, advection, soil water availability, cultivation method and other factors.
Effect of local conditions and agricultural practices
an effective way of characterizing, evaluating and monitoring any irrigation system.
Water Balance
If no rainfall occurs effective rainfall is _____.
zero
ratio of water delivered to the farm to the water diverted from the source multiplied by 100
Water conveyance efficiency, Ec
the ratio of water stored in the root zone during the irrigation to the water delivered to the farm multiplied by 100
Water application efficiency, Ea
the ratio of water beneficially used by the plant to the water delivered multiplied by 100.
Water-use efficiency, Eu
the ratio of water stored in the root zone during the irrigation to the water needed in the root zone prior to irrigation multiplied by 100.
Water storage efficiency, Es
adaptable to rice lands where basins are constructed around one or more trees and flow turned into the basin by means of portable pipes or large hoses.
Basin flooding
ratio of normal consumptive use of water to the net amount of water depleted from root zone.
Consumptive use efficiency, Ecu
Surface Irrigation Methods are
1) Wild flooding
2) Controlled flooding
3) Check flooding
4) Basin flooding
5) border strip irrigation
6) Furrow irrigation
widely used for irrigation of row crops
Furrow irrigation
turning water onto natural slopes without much control or prior preparation such as those pastures and other inexpensive crops.
Wild flooding
the ratio of the average numerical deviation in depth stored during irrigation to the average depth of water stored during irrigation
Water Distribution efficiency, Ed
accomplished using field dikes or by use of BORDERS, CHECKS, and BASINS
Controlled flooding
Type of ________ are some factors to consider when choosing a method of irrigation.
soil, topography, crop and economic considerations
The important parameters in furrow irrigation are
a.) Length and slope of furrow
b.) Water distribution in furrows
c.) Furrow Stream Size
Furrow length varies widely from LESS THAN _____ meters to MORE THAN ___ meters. The slope should preferably be ____ although some soils could have slope of 3 to 6 %.
25, 500, 0.5 to 3%
a number of strips, 10-20 meters wide, are separated by low leeves perpendicular to the slope of the ground. Then the water is turned into the strips wetting the soil as it advances. Size of streams is delivered to a strip may vary from 15 to 300 li/sec depending on the kind of soil, size of the border and the nature of crop
border strip irrigation
consist of turning water into relatively level plots surrounded by leaves as what is normally done for lowland rice production
Check flooding
Corrugations or small furrows are simply narrow ditch between rows of crops with about _______ of surface area wetted during irrigation as compared to flooding method
0.2 to 0.5
A typical sprinkler irrigation system consists of a pumping or pressure system, a main supply line, several lateral lines, vertical riser and sprinklers which can be ____
fixed nozzles or rotating type
A typical sprinkler irrigation system consists of a _______, several ______ which can be fixed nozzles or rotating type
- pumping or pressure system, a main supply line,
- lateral lines, vertical riser and sprinklers
The application of water in the form of spray over the land is accomplished by means of
sprinkler irrigation
sprinkler can be used to control soil ______ and thus ensure FAVORABLE CONDITION for plants.
temperature and humidity
also referred to as TRICKLE IRRIGATION it allows FREQUENT OR SLOW APPLICATION of water either directly on land surface or into the root zones of the crops.
Drip Irrigation Method
The water outlets in the drip irrigation system are called ______ which DISCHARGE A FEW LITERS of water per hour.
emitters
Subsurface irrigation method requires _____ water movement results in MORE EFFICIENT water application
upward
applying water to the soil directly under the ground surface
Sub-irrigation Method
structure located at the head of conveyance canals, main laterals and main farm ditches to control the flow of water
Headgate
The major considerations for determining how much and when to apply irrigation water are: _____
amount of the water needed by the crop, availability of water, and soil moisture storage capacity
Dam which may be an overflow type without spillway or storage type in which a spillway is an added component;
Gates, sluices, river training wall and other appurtenances.
Headwork structures
______ affects every aspect of plant growth. It is the most important factor limiting crop productivity and yield.
Water stress
a) Division boxes at head of laterals and sub-laterals;
b) Turnout to lateral and ditches
Control structures
refers to the amount of water that can be stored between field capacity and the selected maximum moisture tension should be above permanent wilting percentage.
depth
necessary to divert water from a source, convey it to the intended area and control the application or distribution to individual farm lots
Irrigation Structures
the process of determining when irrigate and how much water to apply per irrigation. It is essential for efficient use of water, energy and other production inputs such as fertilizers.
Irrigation Scheduling
Structures in an open
canal system is subdivided in
1) Headwork structures
2) Conveyance structures
3) Control structures
4) Protective structures
5) Combined structures
Structures may be grouped into two categories: those common to gravity irrigation systems such as an _____, and those that are used in pressurized systems such as_______.
open canal network, pipes and sprinklers or drip irrigation systems
a) Flumes across channels, drainage course, or depressions;
b) Inverted siphon under obstructions or across drainage courses, or under farm roads;
Conveyance structures
a) Spillway to prevent overlapping of canal banks;
b) Over chute to carry flood runoff over open channels;
c) Culvert to carry drainage
Protective structures
advantageous to combine checks and turnouts with other structures
Combined structures
structures which raises the water level in the river so that water can be diverted through the conveyance canal
Diversion dam
structure used to raise water to a desired height to enable water to flow to the headworks of the different canal, branching from the main canal, laterals and sublaterals.
Checkgate
– structure which serves as outlet of water in irrigation canals whereby water passes through and discharges into main farm ditch or service area.
Turnout
structures to divide the flow of water at desired directions usually placed or built with the main farm ditch to divert water to supplementary
farmditch.
Division box
structure which crosses waterways to discharge the excess water drained or removed from the field
Drainage crossing
to convey water over the ditch bank into the furrow.
Siphon tubes
conveys canal water under roads or railroads. The minimum recommended clearance between the road and culvert for railroad and road crossing is 0.90 m while for farmroad and thresher crossing is 0.60 m if needed.
Road Crossing
structure constructed or placed along supplementary farmditch at the head of the internal farmditch to control and regulate water flows serving farm or group of farms.
Off-take
are specially shaped, engineered structures that are used to measure the flow of water in open channels.
Flumes
structure at the end of a farmditch to check the direct flow of water to the drainage ditch.
End check
structure constructed across irrigation canals for traffic crossing by man, animal, cart, sleds, or vehicles.
Canal crossing
closed conduit designed to convey canal water in full and under pressure running condition, to convey canal water by gravity under roadways, railways, drainage channels and local depressions.
Inverted siphons
to convey water underneath roads or other obstructions
Culvert
for places where natural slopes down which canals must flow are so high as to cause excessive water velocities & erosion of the canal banks & bed.
Drops & Chutes
used to shorten the length of a diversion canal to avoid difficult & expensive construction on steep, rocky hillsides & to convey water through mountains
Tunnels
The method needs a ______ device with a revolution counter that registers the number of rotation of the meter propeller or cup for a given period.
Current meter method
This velocity area method is easy and practical to employ in the absence of a flow measuring device
Float method
Pumps are hydraulic equipment which may be classified into two types:
a) rotodynamic pumps
b) displacement pumps
water conveying conduit or trough which is supported on abutments by piers.
Elevated flume
Centrifugal pump requires priming before it is started. ______consists of filling the casing with water so that air trapped does not hinder its operation and reduce its efficiency.
Priming
These are the notched opening on structures pace across the canal or creek. They obstruct the flow to create a pond and the water passes over a crest which can be rectangular, triangular or trapezoidal in shape.
Use of sharp crested weirs
in-line canal structure designed to convey canal water from a higher level to a lower level, duly dissipating the excess energy resulting from the drop in elevation.
drop
with rotating element which imparts energy to water (the action is the reverse of a turbine generating hydroelectric power)
rotodynamic pumps
may be used to estimate flood discharge when it is not practical and safe to do direct measurements.
Indirect Measurement Methods
especially designed to measure flow by nothing the head loss caused by forcing a stream of water through a throat or constricted section of the flume with a depressed bottom.
Use of Parshall flume
The opening can be rectangular or circular in shape.
Use of Orifice Opening
include reciprocating type in which a piston draws water into a cylinder on one stroke and forces it out onto the next, and the rotary type which two cams or gears mash together and rotate into opposite directions to force the water continuously past them.
displacement pumps
____ means more power cost and more time required to apply the needed irrigation water. Under usual operating conditions centrifugal pumps have efficiencies between 50 and 85%.
Low efficiency
a channel built with unvarying cross-section and constant bottom slope; otherwise the channel is nonprismatic
Prismatic channel
The overall efficiency of a new electric motor and water pump is about ____. Motor has at least ____ efficiency and the pump about ____.
65%, 95%, 75%
refers to the cross section of a channel taken normal to the direction of flow
Channel section
refers to the vertical distance at which water is lifted. also referred to a STATIC HEAD
Pumping Lifts
a conduit in which water flows with free surface. Open channel can be
Natural channel (UNDERGROUND STREAMS) , which include all watercourses that exist naturally on the earth.
Open channel
is the vertical distance of the lowest point of a channel section from the free surface (or depth of flow section, d)
Depth of flow, y
the cross-sectional area of the flow normal to the direction of flow
Water area, A
the elevation or vertical distance of the free surface above a datum. If the lowest point of the channel section is chosen as the datum, the stage is identical with the depth of flow.
Stage
is the width of channel section at the free surface.
Top width, T
the sum of the pressure head (p/γ) and elevation head (z). For open channel flow (in which the pressure head is zero), the _______ elevation is the same as the water surface elevation.
hydraulic grade
the length of the line of intersection of the channel wetted surface with a cross-sectional plane normal to the direction of flow.
Wetted perimeter, P
measuring the mean flow velocity across section and multiplying it by the area at that point to calculate the flow rate.
Velocity-Area Method
The rate at which energy is lost along a given length of channel ________and is usually presented as a unitless value or in units of length per length
(ft/ft, m/m, etc.).
friction slope
the sum of the hydraulic grade and the velocity head (V^2/2g). This is often referred to as the ________, or EGL. For a lake or reservoir in which the velocity is essentially zero, the EGL is equal to the HGL
energy grade line
the flow rate is calculated by weighing the entire content of the flow stream that was collected in a container for a fixed length of time.
Timed Gravimetric Method
the flow rate is measured by determining how much the flowing water dilutes an added tracer solution
Dilution Method
If F is less than unity, or < square root 𝑔𝐷 , the flow is ______. In this state the role played by gravity forces is more pronounced; so the flow has a low velocity and is often described as tranquil and streaming.
subcritical
Flow Measurement in Open Channels
- Timed Gravimetric Method
- Dilution Method
- Velocity-Area Method
- Hydraulic Structure Method
- Slope-hydraulic Radius-Area Method
if the viscous forces are so strong relative to the inertial forces that viscosity plays a significant part in determining flow behavior.
Laminar flow
if the viscous forces are weak relative to the inertial forces.
Turbulent flow
mixed state between laminar and turbulent states.
Transitional flow
When Froude number is equal to unity (𝑉 = square root 𝑔𝐷) the flow is said to be in a _____
critical state
lined channels and built-up channels that can withstand erosion satisfactorily.
Nonerodible Channel
If F is greater than unity, or 𝑉 > square root 𝑔𝐷, the flow is _______. In this state the inertial forces become dominant; so the flow has a high velocity and is usually described as rapid, shooting and
torrential.
supercritical
The depth of flow must be constant (that is, the hydraulic grade line must be parallel to the channel bed). This depth of flow is called _______.
normal depth
an empirical equation widely used for uniform open channel flow
Manning’s Equation
velocity distribution in an open-channel flow is quite non-uniform because of (1) non-uniform shear stress along the wetted perimeter, (2) presence of free surface on which the shear stress is zero
Velocity Distribution
If the velocity is lower than critical velocity (the depth is greater than critical depth), the flow is ______.
subcritical
the vertical distance from the top of the channel to the water surface at the design condition.
Freeboard
the velocity is higher than critical velocity (that is, the depth is less than critical depth), the flow is considered
supercritical
unlined channels except those excavated in firm foundations, such as rock bed.
Erodible Channel
The nonerodible materials used to form the lining of a channel and the body of a built-up channel include
concrete, stone masonry, steel, cast iron, timber, glass, plastic, etc.
The purpose of lining a channel is in most cases to _____, but occasionally it may be to check seepage losses.
prevent erosion
the channel section having the LEAST WETTED perimeter for a given area has the maximum conveyance; such a section is known as the .
best hydraulic section
the speed at which waves will ripple outward from a pebble tossed into the water.
wave celerity
is a function of the crop’s evapotranspiration and irrigation efficiency which will account for unavoidable losses during water application. It is also known as the CROP DAILY WATER REQUIREMENT (WR).
daily water use rate
a depth for which the specific energy is at a minimum is called the
critical depth.
the capacity of the soil to absorb water and it differs from one soil texture to another Suggested
Soil Intake Rate
an aide in determining the number of sprinkler heads needed and the required number and length of laterals, manifolds, and mainline pipes
Field Layout
______is necessary to make sure that it is capable of
supporting the root system of the crop or crops to be planted. That is, _____ should be greater than or at least equal to the plant root depth.
soil depth
the quantity of water, which should be applied during irrigation in order to replenish the water used by the crop during evapotranspiration.
depth of water application
_____ requirement of the crop determined by subtracting the rainfall (if any) from the peak daily crop water requirements.
peak daily water use
_______ shall be decided based on the extent of field area, source of water and type of sprinkler irrigation system
Sprinkler and lateral spacing
the time it takes the crop to deplete the soil moisture at a given soil moisture depletion level.
Irrigation frequency
